1. Filed of the Invention
The present invention relates to a light beam profile transforming element, and a process for manufacturing the element.
2. Description of the Related Art
Due to recent developments in optical fiber technologies, laser light sources and the like, optical communication and systems and devices to which an optics technology is applied are more widely used.
In particular, the optical interconnection technology between an optical element such as a light emitting element or a light-detecting element and an optical fiber, used in optical communication, is very critical to the level of propagation loss, i.e., the transmittable distance. Generally, the optical interconnection is made by inserting a micro-spherical lens between an optical fiber and an optical element, or by processing an end of an optical fiber to form a convex lens. Since these optical parts used for the optical interconnection are extremely small, the machining or processing, as well as handling, require great skill, and thus they are not satisfactory. Therefore, a monolith solid optical interconnection element is sought, from the viewpoint of a matching preciseness, machining or handling, and long term reliability, etc.
FIG. 1 shows a typical optical beam profile transforming element of the prior art.
Generally, the beam profile of light emitted from a semiconductor laser is not circular but is elongated in the direction parallel to the active semiconductor layer, for example, an ellipse having a long diameter of about 4 .mu.m and a short diameter of about 1.5 .mu.m as shown by (a) in FIG. 1. On the other hand, the core of an optical fiber is circular in section. Therefore, if a semiconductor laser is connected directly to an optical fiber, the light is not transmitted with a satisfactory efficiency.
To solve the above problem, as shown in FIG. 1, a combination of a cylindrical lens 7 and a convergent rod lens is most often used. The cylindrical lens 7 first transforms the ellipse beam emitted from the semiconductor laser 6 to a circular beam (b) and the circular beam (b) is then transformed by the convergent rod lens 8 into a circular beam (c) having a diameter matching that of the core 90 of an optical fiber 9. This assembly has an advantage in that it can be composed of optical parts now in practical use, but has disadvantages such as the need for a large number of component parts including holders, and special skills required for the assembling, further, the time required for matching the axes of optical parts, etc.
Single-mode optical fibers recently used for a long distance optical communication have an outer diameter of about 125 .mu.m and a core of at largest 10 .mu.m in diameter. On the other hand, the above assembly of the prior art comprises a large number of component parts, and the axis matching between a semiconductor laser, lenses and an optical fiber must be precise to within a few micrometers. As a result, great skill, a number of costly parts, and too many steps are disadvantageously required.